1. Field of the Invention
This invention relates to foamable siloxane compositions which yield, upon cure, silicone foams having decreased friability. The decreased friability of these foams is provided by the use of a silicone resin copolymer. The friability of the foam that results when a composition of the present invention is cured is comparable to or less than the friability of silicone foams found in the art, but have the benefit of being of lower density and of being less expensive to prepare. This invention also relates to silicone foams prepared from such foamable siloxane compositions. This invention also relates to a method of using the siloxane foams of the present invention to weather-strip windows and doors.
2. Description of the Related Art
In U.S. Pat. No. 4,026,835, Lee et al. teach a method of preparing a heat curable organosiloxane foam comprising an organohydrogensiloxane, a hydroxylated organosiloxane and a rhodium catalyst.
In U.S. Pat. No. 4,495,227. Tanaka teaches a foamable silicone-containing composition comprising a liquid diorganopolysiloxane with at least two functional groups which may be hydroxyl groups, a liquid organosilicon compound with at least three functional groups which may be hydrogen atoms, a condensation catalyst and a blowing agent which is an encapsulated low-boiling organic liquid.
In U.S. Pat. No. 4,555,529, Lee et al. teach a foamable polyorganosiloxane composition consisting essentially of a vinyl-containing polydimethylsiloxane, an organohydrogensiloxane, a platinum catalyst, a foam stabilizer and a blowing agent that can be compressed or liquefied at moderate pressures
In U.S. Pat. No. 4,593,049, Bauman et al. teach a method of producing an elastomeric silicone foam said method consisting of mixing a vinyl-containing polydiorganosiloxane, a hydroxylated polydiorganosiloxane, a platinum catalyst, an organohydrogensiloxane, a foam stabilizer and optionally an alcohol and allowing the mixture to form a froth and cure.
In U.S. Pat. No. 4,599,367, Bauman et al. teach an open-cell silicone foam composition comprising a hydroxyl-terminated polydiorganosiloxane, a silicon hydride, water, a platinum catalyst, and optionally a foam stabilizer and/or an alcohol.
In U.S. Pat. No. 4,631,299, Laisney et al. teach an organopolysiloxane composition comprising a vinyl-containing diorganopolysiloxane having a viscosity of 100 to 250,000 mPa.s, a dimethylpolyorganosiloxane having a viscosity of 10 to 5000 mPa.s., a hydroxyl-containing diorganopolysiloxane having a viscosity of 5 to 10,000 mPa.s, a liquid resin, a liquid organohydrogensiloxane, a filler and a platinum catalyst.
In U.S. Pat. No. 4,728,567, Razzano et al. teach a silicone foam composition comprising an organohydrogensiloxane, a hydroxylated organosiloxane and a platinum catalyst.
In U.S. Pat. No. 4,888,217, Jones teaches a foamable silicone composition comprising as its sole components an alkyl-hydrogen-siloxane unit-containing polysiloxane, a hydroxyl-containing polysiloxane, a compound containing a carbon bonded hydroxyl group, a polyorganosiloxane and a platinum catalyst.
The compositions of the present invention, unlike the compositions described above, contain a silicone resin copolymer and a hydroxyl-containing siloxane polymer and yield, upon cure, silicone foams having reduced friability.